1. Field
Embodiments of the invention relate generally to recovering liquid hydrocarbons from subterranean reservoir with an injectate, and more particularly to methods and systems to design the injectate to reduce surface complexation between interfaces of the liquid hydrocarbon and reservoir rock.
2. Background Information
Oil, petroleum, tars, other liquid fossil fuels, and other liquid hydrocarbons are contained in, and recovered from, subterranean or underground formations. To access these liquid hydrocarbons, wells are typically drilled from the surface down into the subterranean formations, and the liquid hydrocarbons are recovered through the wells:
Initially, the liquid hydrocarbons may be recovered through primary extraction. Primary extraction may use natural reservoir pressure to force the liquid hydrocarbons into the well. However, typically not all of the liquid hydrocarbons may be recovered through primary extraction. At some point, residual liquid hydrocarbons may be held too tightly within the subterranean formation (e.g., due to adhesive interactions between the oil and the rock) and may be unrecoverable or practically unrecoverable through primary extraction. Often the amount of remaining liquid hydrocarbons may be significant, for example around half of the original oil or other liquid hydrocarbons.
Secondary extraction is commonly used in order to recover some of the remaining liquid hydrocarbons. A common form of secondary extraction involves injecting a medium known as an injectate, such as water (e.g., seawater or terrestrial water) or gas (e.g., carbon dioxide), into the subterranean reservoir in order to mobilize and recover additional liquid hydrocarbons.
FIG. 1 is cross-sectional side view illustrating an example of a prior art waterflooding procedure. An injection well 101 resides on a surface 102 of the earth 100. An injection wellbore 103 extends from the injection well 101 into a subterranean formation 104. The subterranean formation may be, for example, sedimentary rock (e.g., sandstone, siltstone, etc.), carbonate (e.g., limestone, dolomite, etc.) or another portion of the earth having oil, petroleum, tars, other liquid fossil fuels, or other liquid carbonaceous fuels or hydrocarbons, contained within pores or openings thereof.
During a waterflooding procedure, waterflooding equipment 105 may be used to pump, inject, or otherwise introduce liquid injectate 106 (e.g., seawater or terrestrial water) under pressure through the injection well 101 into the injection wellbore 103 and down into the subterranean formation 104. Without limitation, the waterflooding equipment 105 may include a high pressure pump, storage tanks, storage trucks, piping, etc. The injectate 106 may mobilize and drive a portion of the remaining liquid hydrocarbons toward the production well 109. An injectate/hydrocarbon mixture 107 (also including some aqueous connate fluid natively present in the subterranean formation along with the hydrocarbon) may be recovered through a production wellbore 108 and the production well 109.
Traditionally, the liquid injectate used for waterflooding has typically been substantially unmodified seawater or terrestrial water (e.g., from lakes, streams, or wells), which is available at the site of the injection well 101. More recently, there have been reports that, under certain circumstances, the salinity of the injectate 106 used in the waterflooding operation affects the performance of the waterflooding operation (e.g., the amount of additional oil recovered). In particular, it has been reported that, under certain circumstances, low salinity injectate or so-called “low-sal” water flooding operations may increase the level of hydrocarbon recovery as compared to the use of higher salinity injectate.